For the sponge cake roll, preheat the oven and beat the egg whites. Meanwhile, add 50 g of sugar until the egg whites are beaten stiff. Mix the remaining sugar and the egg yolks in a bowl until foamy.
Add the beaten egg whites to the bowl first, followed by the sifted flour and cornstarch. Gently fold in with a mixing spoon. Line a baking tray with baking paper and spread the batter evenly on it.
Bake at 200°C top/bottom heat for about 8 minutes. Then turn out onto a kitchen towel and roll up. Let cool down well.
Finally, unroll the roulade again and remove the kitchen towel. Spread with jam. Then roll up again and decorate the sponge cake roulade with powdered sugar.